Conventionally, as a method of transferring a toner image carried on an electrophotographic photoreceptor (hereinafter also referred to simply as a photoreceptor) to a recording material, an image forming method employing an intermediate transfer member has been known. In such a method, a final image is formed as follows: in a process in which a toner image is transferred from an electrophotographic photoreceptor to a recording material, another transfer process is provided wherein a toner image is primarily transferred from an electrophotographic photoreceptor to an intermediate transfer member and then the primary transferred image carried on the intermediate transfer member is secondarily transferred to a recording material. This method is often employed as a multiple transfer method for each color toner image in a so-called full color image forming apparatus which reproduces a color-separated original image via subtractive color mixing using such as a black toner, a cyan toner, a magenta toner, and a yellow toner.
However, in such a multiple transfer method employing the intermediate transfer member, image defects tend to occur due to the transfer failure of an toner image, since two processes, namely, the primary and the secondary transfer process, are carried out and also toners of four colors are superimposed on the transfer member.
It is generally known that transfer efficiency can be enhanced via surface treatment of a toner with an external additive such as silica against toner transfer failure. However, there are noted problems in that no adequate transfer efficiency is realized since silica is liable to be released from the toner surface and also to be buried into the interior of the toner due to the stress from a stirring member for the toner in the development device; the stress from a regulation blade to form a toner layer on the development roller; or the stress caused between the photoreceptor and the development roller. Therefore, a cleaning device is needed to scrape a toner remaining on the intermediate transfer member using a blade.
To overcome such problems, methods of forming a releasing layer on the surface of the intermediate transfer member have been proposed as described below. To enhance releasability of a toner from the intermediate transfer member, a silicon oxide layer or an aluminum oxide layer is formed on the intermediate transfer member (refer to Patent Document 1).
Further, a method of forming an inorganic coating layer on the intermediate transfer member has been proposed (refer to Patent Document 2).
Patent Document 1: Unexamined Japanese Patent Application Publication (hereinafter referred to as JP-A) No. 9-212004
Patent Document 2: JP-A No. 2000-206801